The following descriptions relate to a rotation mechanism for an endoscope.
Generally, at an operation section of an endoscope, rotation mechanisms such as a mechanism for operating a bending portion of an insertion section of the endoscope, a mechanism for changing a rising angle of a treatment tool and the like are provided. Such a mechanism is configured such that an operating member (i.e., a rotating member) is rotatably supported by a shaft member, and a thrust stopper for preventing the operating member from being removed from the shaft member is provided at the distal end portion of the shaft member. Examples of such a structure are disclosed in Japanese Patent Provisional Publications No. 2003-135384 (hereinafter, referred to as '384 publication) and No. HEI 11-47082 (hereinafter, referred to as '082 publication).
Specifically, according to '384 publication, the thrust stopper contacting an distal end surface of the shaft member is secured thereto with a screw. According to '082 publication, a C-ring or an E-ring is engaged in a groove formed, at the distal end portion, on the circumferential surface of the shaft member. In either case, the position, in the axial direction of the shaft member, of the thrust stopper is fixed due to the structure of the shaft member.
At the distal end portion of the shaft member, which is remote from the proximal end that is secured to a frame of the operation unit of the endoscope, there may exist a dimensional error greater than expected tolerance since accumulated errors exhibit at the distal end portion. In such a case, the position of the thrust stopper with respect to the rotational member varies, and the rotational member may have a play in the axial direction (i.e., thrust direction) or the position of the thrust stopper is closer to the proximal end so that the rotational member does not rotate smoothly as the stopper urges the rotational member against the shaft member.